Arakne / Araknemu

 * This file is part of Araknemu.

 *

 * Araknemu is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * Araknemu is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with Araknemu.  If not, see <https://www.gnu.org/licenses/>.

 *

 * Copyright (c) 2017-2021 Vincent Quatrevieux

 */

package fr.quatrevieux.araknemu.game;

import fr.quatrevieux.araknemu.core.event.Dispatcher;

import fr.quatrevieux.araknemu.core.event.EventsSubscriber;

import fr.quatrevieux.araknemu.core.event.Listener;

import fr.quatrevieux.araknemu.game.event.GameSaved;

import fr.quatrevieux.araknemu.game.event.GameStopped;

import fr.quatrevieux.araknemu.game.event.SavingGame;

import fr.quatrevieux.araknemu.game.player.GamePlayer;

import fr.quatrevieux.araknemu.game.player.PlayerService;

import fr.quatrevieux.araknemu.util.ExecutorFactory;

import org.apache.logging.log4j.Logger;

import java.time.Duration;

import java.util.concurrent.ScheduledExecutorService;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.atomic.AtomicBoolean;

/**

 * Handle world saving

 */

public final class SavingService implements EventsSubscriber, PreloadableService {

    private final PlayerService playerService;

    private final GameConfiguration configuration;

    private final Dispatcher dispatcher;

    private final AtomicBoolean inProgress = new AtomicBoolean(false);

    private final ScheduledExecutorService executor = ExecutorFactory.createSingleThread();

    public SavingService(PlayerService playerService, GameConfiguration configuration, Dispatcher dispatcher) {

        this.playerService = playerService;

        this.configuration = configuration;

        this.dispatcher = dispatcher;

    }

    @Override

    public void init(Logger logger) {

        if (!configuration.autosaveEnabled()) {

            return;

        }

        scheduleNextSave();

    }

    @Override

    public Listener[] listeners() {

        return new Listener[] {

            new Listener<GameStopped>() {

                @Override

                public void on(GameStopped event) {

                    executor.shutdownNow();

                }

                @Override

                public Class<GameStopped> event() {

                    return GameStopped.class;

                }

            },

        };

    }

    /**

     * Execute the save

     * Note: this method is non-blocking : the save process is launched in a thread

     *

     * @return true is the save is launched, or false if it's already in progress

     */

    public boolean execute() {

        if (inProgress.getAndSet(true)) {

            return false;

        }

        executor.execute(this::runSave);

        return true;

    }

    /**

     * Schedule the next autosave

     *

     * Note: do not use {@link ScheduledExecutorService#scheduleAtFixedRate(Runnable, long, long, TimeUnit)}

     *       to prevent conflicts on long run. Instead, it will reschedule a save after the previous one

     */

    private void scheduleNextSave() {

        if (executor.isShutdown()) {

            return;

        }

        final Duration interval = configuration.autosaveInterval();

        executor.schedule(() -> {

            if (!inProgress.getAndSet(true)) {

                runSave();

            }

            scheduleNextSave();

        }, interval.toMillis(), TimeUnit.MILLISECONDS);

    }

    /**

     * Run the save process

     * Note: this method will not check the "inProgress" property : it must be checked before

     */

    private void runSave() {

        dispatcher.dispatch(new SavingGame());

        try {

            playerService.online().forEach(GamePlayer::save);

        } finally {

            inProgress.set(false);

            dispatcher.dispatch(new GameSaved());

        }

    }

}